Top stringer in a drift chamber for CLAS12 project
A top stringer work instructions
Top stringer responsibles
1- Dropping a wire from the top feed through to the bottom feed. The wire should extend beyond the bottom feed through a distance of 10-12" relative to the bottom feed through's crimp pin final location.
2- Crimp the pin that holds the wire in the top feed through.
3- Observe if any changes take place inside the chamber through the stringing time.
The top stringer has tools such as chains (hand made), a wire cutter, a crimper, torch, and a feeler gauge. A lift is used to help the top stringer to reach the top of the chamber, the chamber is placed to take advantage of the gravity to vertically drop the wire inside it.
Procedure to drop the wire inside the chamber
The chamber location is in a clean room, before following the next procedure, the stringer is expected to follow all the clean room instructions that include safety instructions to be in a clean and safe working environment for him (her) and the other co-workers.
The top stringer is going to :
1- locate then Raise up the lift to a height that helps to see the all the top and top feed through rows that he is going to string. he/she should distinguish their locations and their numbers (The rows are numbered for accuracy). the lift located enough distance away from the chamber to avoid any direct touch with it.
2- Be sure that the stringing machine is in an appropriate location (the bottom stringer helps to relocate if needed), and the wire is stretched around the machine's pulleys.
3- Check the crimper's gap using the feeler gauge (gaper). Crimper's jaws should touch the feeler gauge but not to press on it.
3- Clean the hands using alcohol in case of touching unclean surfaces.
4- Feed the free end of wire gently into the plastic cylinder by holding the chain with the dominant hand and the plastic cylinder with the other hand, then feed the needle of chain gently in the plastic cylinder with the wire to a distance that prevent any of them to separate as they are dropped inside the chamber.
4- Extend the wire by pressing the bottom of the machine until the top of the chain passes through the top feed through with a distance of 1-2" (or shorter if possible) from the inside end of the top feed through. Clicking the machine bottom with the least pressure.
5- Wait until the chain is stable. The amplitude of the chains' swings should be less than the distance between adjacent wires before you attempt to drop the wire.
6- Increase the length of the wire until the wire reaches the inside end of the bottom feed through.
7- Two ways to feed the wire inside the bottom feed through:
a- By holding and extending wire closer to the machine, then feeding the wire slowly in the feed (specially for sense wires).
b- Feed the wire in the bottom feed through directly. (for guard and field wires).
Feeding the wire continues until the chain disappears, then stop.
It is recommended to feed wire all over the feed through continuously until the chain comes of it to avoid having the chain stopped inside it.
At this moment, if the wire passes the feed through, it will be stretched the stringer won't observe any wire bending inside the chamber.
8- Extend the wire to have additional length of 10-12" outside the bottom feed through. Counting is used to reach the desired length.
9- Insert a crimp pin in the wire, then place it inside the feed through (by hand or the top end of the crimper), them crimp it with a little push inside the feed through. the pin has to be vertical to the feed through plane as much as possible.
The crimping location is directly above the top end of the feed through.